This invention relates to an automatic weighing apparatus and, more particularly, to the arrangement of devices for opening the gates of hoppers in an automatic weighing apparatus.
A known automatic weighing apparatus of the combinatorial weighing type has a plurality of weighing machines disposed on a circle surrounding a unit which supplies articles to be weighed, and operates by supplying weighing hoppers, which are associated with respective ones of the weighing machines, with the articles from the supply unit, combining the weight values provided by the weighing machines into a number of different combinations and finding the total weight value of each combination, selecting a so-called "optimum combination" of weighing machines to obtain a predetermined weight from among the total weight values of the combinations, discharging only the articles contained in the weighing hoppers of the selected weighing machines, and collecting the discharged articles to provide a batch of the articles having the predetermined weight. In order for the weighing hoppers of the selected weighing machines to discharge their articles and be resupplied with articles from overlying pool hoppers to prepare for the next weighing cycle, the automatic weighing apparatus is provided with devices for opening the gates of the designated weighing and pool hoppers each weighing cycle.
In the conventional automatic weighing apparatus of the above-described type, the hopper gate opening devices are arrayed in a circular configuration about the hoppers, and they are themselves large in size even if arranged inside the hoppers, thereby increasing the overall size of the apparatus and, hence, requiring a large amount of space for installation. In addition, the weighing hoppers and pool hoppers must be detached from the weighing apparatus for periodic cleaning or whenever cleaning is required. However, since the hopper gate opening devices are situated on the outer periphery of the weighing apparatus, detaching and then reattaching the hoppers is an extremely troublesome operation.
My copending application, Ser. No. 659,762 discloses a hopper gate opening device including a drive mechanism in which a follower roller which follows the cam surface of a cam is connected to a push rod. The push rod is biased in the direction of the cam by a return spring so that the follower roller is abutted against the cam surface owing to the biasing force. The push rod is reciprocated by rotation of the cam to open and close the gate of the corresponding hopper. In the drive mechanism of the type described, the cam is rotated at high speed in order to perform a rapid weighing operation. When the cam is rotated at high speed, however, the biasing force of the return spring alone is insufficient to provide a reliable follow-up capability, and the follower member tends to part from the cam surface. This is a source of erroneous operation and results in considerable noise and vibration.